Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$109.53	8.372%	$118.6999	$118.70	$118.70	$118.70
Purchase #2	$192.61	13.444%	$218.5045	$218.50	$218.50	$218.50
Purchase #3	$55.76	6.422%	$59.3409	$59.34	$59.35	$59.30
Purchase #4	$127.41	7.231%	$136.623	$136.62	$136.60	$136.60
Purchase #5	$193.63	13.206%	$219.2008	$219.20	$219.20	$219.20
Purchase #6	$193.41	3.488%	$200.1561	$200.16	$200.15	$200.20
Purchase #7	$124.39	5.418%	$131.1295	$131.13	$131.15	$131.10
7 purchase totals =	$996.74		$1,083.6547	$1,083.65	$1,083.65	$1,083.60